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Edible-Pod Peas

Pisum sativum

Last revised January 3, 2003

Seeding o Fertilizers o Harvesting, Handling, Storage o Pest Control: Diseases, Insects, Weeds


The Oriental edible-pod pea or Chinese Pod Pea is also known as Snow Pea and Sugar Pea. These are all flat-podded peas that are hand picked and are available fresh or as a frozen vegetable and used in Oriental dishes.

A relatively new type of pod pea known as the Snap Pea has been developed in the U.S.A. by Dr. C. Lamborn of Gallatin Valley Seed Co. (now Rogers NK Seed Co.). It is finding increasing popularity in the home garden and as a new processed vegetable. All are round-podded similar to standard pea pods in appearance, but more fleshy and free from pod-wall fiber when mature; some are also stringless. Bush and pole types are also available. Only the bush-stringless type is used by the processing industry, since these can be machine harvested. These peas can also be purchased fresh or as a processed specialty vegetable and used in traditional cooking.

Stringlessness in peas is available in a number of varieties; however, the stringless character may be nullified by even a few days of cool temperatures. Reports indicate that even 2 days of day temperatures below 70 F occurring when seeds begin to swell in the pods, will cause strings to develop in otherwise stringless varieties currently available. The stringless character is associated with reduced vigor, plant size and yield, but is an important quality character.


VARIETIES (approximately 100 days).

Oriental Pod types (thin, flat, edible pods): Oregon Sugar Pod II (bush type, and leaf roll, powdery mildew, and enation virus resistant), Oregon Giant (powdery mildew and enation virus resistant with pods larger than Oregon Sugar Pod II). For trial: Dwarf Gray Sugar, Mammoth Melting Sugar (requires trellis), Nippon Kinusage, Nofilla (stringless), Norli (stringless). For processing, processors will specify varieties.

Snap Pea types (round fleshy edible pods):

"Bush" types for processing: Only "bush," stringless types are used (see comment above about reversion to "strings" under cool temperatures). Processors will specify varieties for each planting period. Some varieties are proprietary and available only under special agreement with the seed company. Stringless varieties publicly available at this time: Sugar Daddy. The variety Sugar Pop is limited in availability and is adapted to cool regions only; vegetative growth and fruitfulness are severely curtailed by warm temperatures.

A number of new afila (modified leaf) snap pea varieties are available. These may have particular adaptation west of the Cascades, where successful snap pea production for processing has been difficult with standard leaf types. Standard types can easily lodge and mat and develop mold during periods of wet weather at harvest. Afila types maintain an erect, interlocked, plant habit that allows good air movement through the canopy and reduces risk from lodging and mold. These have been developed by Novartis (Rogers Seed).

Other "bush" snap pea varieties (which do develop strings) are: Early Snap and Sugar Bon (early); Cascadia and Sugar Ray (enation virus resistant); Sugar Mel, Super Sugar Mel, Sugar Ann, and Snappy.

Pole type: Super Sugar Snap (mildew resistant).

Strings develop at different rates and to different degrees in snap pea varieties.


SOIL AND LAND PREPARATION

It is important to choose a field with uniform fertility, soil type, slope, and drainage to get a uniform, edible pea crop. The best soils are silt loams, sandy loams, or clay loams. Edible pod peas need a good supply of available soil moisture, but yields may be reduced by over-irrigating as well as under-irrigating. Peas grown on wet soils develop shallow root systems which cannot supply the plant's water requirements when the soil dries out later in the season. Root rot is often a problem in wet soils.

Determine corrective lime and fertilizer needs by a soil test. Adjust pH to 6.5 or higher for maximum yields.

Edible pod peas germinate well under cool soil temperatures. Good germination will occur at 39 to 57 F.

The land should be plowed, harrowed, and a cultipacker used lightly to ensure a firm seedbed. The land should be level to make harvesting more efficient.


SPACINGS

For machine harvest, standard pea production spacing of 6 to 8 inches between rows is used with seeds spaced about 2 inches apart in the row. Machine harvest has only been partially successful with Oriental peas, but is used with bush, stringless, snap peas used for processing.

For fresh market, rows are trellised and harvested daily or every other day for several weeks. Rows are spaced 5 to 6 feet apart with plants about 2 inches apart in the row.


SCHEDULING PLANTINGS

Plantings may be made as soon as the soil can be worked in the spring. Enation resistant varieties may be planted throughout the entire planting season. Terminate the use of susceptible varieties by April 1 (see variety list and Disease Control section). Plantings must be staggered to allow for orderly harvest. For continuous hand harvest, new plantings should be made every 7-14 days, with early plantings staggered apart more days than later ones. Plant the amount of area that would be picked over that period of time. Processing edible pod peas are scheduled on the basis of heat units. The processing company establishes the planting and harvest schedules.

Fresh market edible-pod peas may be scheduled on the basis of heat units and by picking requirements for given plantings. In general, April plantings will require about 70 days to harvest, May plantings about 60 days and June plantings about 55 days. Plantings are staggered so as to allow peak harvest of a planting for about 2 weeks before the next planting comes into peak production.


SEEDING

Snap peas: Snap pea seed numbers approximately 90-175 per ounce. For plantings intended for machine harvest and processing, drill dwarf types at a uniform depth of l.5-2 inches into moisture, dropping 3 to 6 seeds per foot of row with rows 6-8 inches apart. Aim for a plant population of 450,000 to 480,000 plants per acre and avoid excessive overlaps and double planting along the edges of the field. This may cause uneven colored peas and lack of uniformity at harvest. Snap peas tend to be more viney than standard peas, so care must be taken not to over-crowd or over-fertilize plantings.

When Oriental pod peas and snap peas are intended for hand harvest, plant in rows 36 inches apart with seeds 1-2 inches in the row for ease of picking. About 50 to 60 lb of seed would be needed per acre. Varieties like Mammoth Melting Sugar Oriental pod pea, and the snap pea variety Sugar Snap can be picked for up to 4 weeks and should be grown on 5-6 foot trellises.

Providing moisture is adequate and not excessive, a light rolling may be advantageous. Heavy rolling or packing is likely to reduce root growth, fertilizer uptake and pea root nodulation, and to increase the number of plants affected by root rot. Inoculate with Rhizobium bacteria in a planter box treatment when planting on soils not previously planted to peas.

New research in conventional peas indicates that stand and seedling vigor can be greatly reduced by the presence of hollow heart (or cavitation) in the seed. This is a physiological disorder believed to be aggravated by premature combining or swathing of the seed crop. Differences in severity by variety and seed source can be large. The range of seed affected was from 5% to 78% with a mean incidence of 33% in a 1986 seed sampling study, and 4% to 75% with a mean incidence of 30% in a 1985 study. It may be that edible pod pea varieties may be similarly affected.


FERTILIZER

Good management practices are essential if optimum fertilizer responses are to be realized. These practices include use of recommended edible pod pea varieties, selection of adapted soils, weed control, disease and insect control, good seed bed preparation, proper seeding methods, and timely harvest.

Because of the influence of soil type, climatic conditions, and cultural practices, crop response from fertilizer may not always be accurately predicted. Soil test results, field experience, and knowledge of specific crop requirements help determine the nutrients needed and the rate of application.

The fertilizer application for vegetable crops should insure adequate levels of all nutrients. Optimum fertilization is essential for top quality and yields. Recommended soil sampling procedures should be followed in order to estimate fertilizer needs. The Oregon State University Extension Service agent in your county can provide you with soil sampling instructions and soil sample bags and information sheets.

Western Oregon:

NITROGEN (N)

Rates of 20 to 30 lb N/A banded with P and possibly K at planting time are suggested. Information on the application of N is given below in the sections on P and K.

INOCULATION

Edible pod pea seed should be inoculated immediately before seeding to insure an adequate supply of nitrogen-fixing bacteria. A fresh, effective, live culture of the correct strain of Rhizobium should be used. In some of the soils in eastern Oregon where peas have been grown for many years, inoculation may not be necessary.

PHOSPHORUS (P)

Phosphorus is essential for vigorous early growth of seedlings. Preferably P, N, and, where required, up to 60 lb K2O/A should be applied in a band 2 inches to the side and 2 inches below the seed at planting time.

When banding equipment is not available 20 to 30 lb N/A and 40 to 80 lb P2O5/A can be drilled with the seed. Additional P2O5 and K2O, when required, can be broadcast and plowed down prior to planting.

             If the soil test*            Apply this amount of
            for P reads (ppm):          phosphate (P2O5) (lb/A):
                  0 - 15                       120 - 150
                 15 - 60                        80 - 120
                 over 60                        40 -  80
*Assumes extraction procedures similar to those used by the OSU Central Analytical Laboratory. Specific information on soil test procedures is available from the Dept. of Crop and Soil Science.

POTASSIUM (K)

Potassium should be applied and plowed down before planting or banded at planting time as described in the above section on P. Potassium should not be included with N and P when fertilizer is drilled with the seed. In a 2" x 2" band application of N, P, and K the K rate should not exceed 60 lb K2O per acre. Additional K, where required, should be broadcast and plowed down prior to planting.

Seedling injury from banded fertilizers tends to be more serious:
- in drier soils
- in coarse textured, sandy soils
- where fertilizer band is close to seed.

Phosphorus fertilizers are less injurious to seedlings than N and K fertilizers.

              If the soil test*          Apply this amount of
             for K reads (ppm):              K2O (lb/A):
                   0 - 100                     90 - 120
                  75 - 150                     60 -  90
                 150 - 200                     40 -  60
*Assumes extraction procedures similar to those used by the OSU Central Analytical Laboratory. Specific information on soil test procedures is available from the Dept. of Crop and Soil Science.

SULFUR (S)

Plants absorb S in the form of sulfate. Fertilizer materials supply S in the form of sulfate and elemental S. Elemental S must convert to sulfate in the soil before the S becomes available to plants. The conversion of elemental S to sulfate is usually rapid for fine ground (less than 40 mesh) material in warm moist soil.

Sulfur in the sulfate form can be applied at planting time. Some S fertilizer materials such as elemental S and ammonium sulfate have an acidifying effect on soil. Sulfur is sometimes contained in fertilizers used to supply other nutrients such as N, P, and K, but may not be present in sufficient quantity.

Responses to S fertilization may not occur for a period of at least 4 or 5 years on "red hill" soils that have a history of high S fertilization. These soils have a comparatively high ability to adsorb S and frequently have a history of high S fertilization through the use of S-containing fertilizer such as ammonium sulfate.

The S requirements of edible pod peas can be provided by:

  1. The application of 20-30 lb S/A in the form of sulfate at or prior to seeding.
  2. Applying 30-40 lb S/A as fine ground (finer than 40 mesh) elemental S the preceding year.
  3. Applying coarser ground elemental S at higher rates and less frequently.
MAGNESIUM (Mg)

When the soil test value is below 0.5 meq Mg/100g or when calcium (Ca) is 10 times more than the Mg apply 10 to 15 lb Mg/A banded at planting.

Magnesium can also be supplied in dolomite which is a liming material and reduces soil acidity to about the same degree as ground limestone. Dolomite should be mixed into the seedbed at least several weeks in advance of seeding and preferably during the preceding year. An application of dolomite is effective for several years.

OTHER NUTRIENTS

Responses of edible pod peas to nutrients other than those discussed in this guide have not been observed in western Oregon. Edible pod peas have a comparatively low requirement for boron. Boron should never be included in banded fertilizer.

LIME

Edible pod peas are fairly sensitive to soil acidity and are responsive to liming of acid soils. Lime application is suggested when the soil pH is 6.0 or below, or when calcium (Ca) levels are below 5 meq Ca/100g of soil.

             If the SMP Buffer*          Apply this amount
            test for lime reads:           of lime (T/A):
                 below 5.5                         6
                 5.5 - 5.7                     5 - 6
                 5.7 - 5.9                     4 - 5
                 5.9 - 6.1                     3 - 4
                 6.1 - 6.3                     2 - 3
                 6.3 - 6.5                     1 - 2
                  over 6.5                         0
*Assumes extraction procedures similar to those used by the OSU Central Analytical Laboratory. Specific information on soil test procedures is available from the Dept. of Crop and Soil Science.

The suggested liming rate is based on 100 score lime. Apply lime at least several weeks before seeding and preferably the preceding year and mix with the surface 5 to 6 inches of soil. A lime application is effective over several years.

Some soils may have a fairly high SMP buffer value (over 6.5) and a low pH (below 5.5). This condition can be caused by the application of acidifying fertilizer. In this case the low pH value is temporary and the pH of the soil will increase as the fertilizer completes its reaction with the soil. This temporary "active" acidity from fertilizer is encountered following recent applications of most N fertilizer materials. Acidifying fertilizers also have a long-term acidifying effect on soil that is cumulative and leads to lower SMP buffer readings.

Sandy soils to which fertilizers have not been recently applied sometimes have both low pH and high SMP buffer values. In such cases, a light application of 1 to 2 T lime/A should suffice to neutralize soil acidity.

For acid soils low in Mg (less than 0.8 meq Mg/100g of soil) 1 T/A dolomite lime can be used as a Mg source. Dolomite and ground limestone have about the same ability to neutralize soil acidity.

Fertilizer Guide #3, "Liming Materials for Oregon," which is available from your local OSU Extension Office, provides additional information on lime.

Eastern Oregon:

NITROGEN (N)

Rates of 15 to 20 lb N/A banded with P and possibly K at planting time are suggested. Information on the application of N is given below in the sections on P and K.

PHOSPHORUS (P)

Phosphorus is essential for vigorous early growth of seedlings. Preferably P, N, and, where required, up to 60 lb K2O/A should be applied in a band 2 inches to the side and 2 inches below the seed at planting time.

When banding equipment is not available 15 to 20 lb N/A and 40 to 75 lb P2O5/A can be drilled with the seed. Do not use urea or diammonium phosphate as N and P sources when fertilizer is drilled with the seed. Additional P2O5 and K2O when required can be broadcast and plowed down prior to planting.

      If the soil test*            Apply this amount of
     for P reads (ppm):          phosphate (P2O5) (lb/A):
           0 - 10                        40 - 120
          10 - 20                         0 -  60
          over 20                          None
*Assumes extraction procedures similar to those used by the OSU Central Analytical Laboratory. Specific information on soil test procedures is available from the Dept. of Crop and Soil Science.

POTASSIUM (K)

Soil testing should be used to evaluate the need for K fertilizer.

       If the soil test*          Apply this amount of
      for K reads (ppm):              K2O (lb/A):
             0 -  75                    90 - 120
            75 - 150                    60 -  90
           150 - 200                    40 -  60
            Over 200                      None
*Assumes extraction procedures similar to those used by the OSU Central Analytical Laboratory. Specific information on soil test procedures is available from the Dept. of Crop and Soil Science.

Potassium should be applied and plowed down before planting or banded at planting time. Potassium should not be included with N and P when fertilizer is drilled with the seed. In a 2" x 2" band application of N, P, and K the K rate should not exceed 60 lbs K2 O per acre. Additional K, where required, should be broadcast and plowed down prior to planting.

SULFUR (S) and OTHER NUTRIENTS: see above under Western Oregon

LIME

Significant responses of edible pod peas to lime have not been observed in eastern Oregon. Edible pod peas are sensitive to soil acidity, however, and the application of lime at 1 to 2 T/A may be considered when the soil pH is below 6.0. Lime should be applied at least several weeks before seeding and mixed with the surface 6" of soil. A lime application is effective for several years.

Fertilizer Guide #3, "Liming Materials for Oregon," which is available from your local OSU Extension Office, provides additional information on lime.

MANURE

Manures contain variable amounts of all plant nutrients. All of the nutrients in manure are not completely available the first year. The following table gives the approximate average content of some nutrients in fresh manures:

     Kind of manure   % Nutrient and % water content

                       Water    N*       P2O5      K2O

     Dairy              87     0.50      0.16      0.44
     Beef               82     0.65      0.43      0.53
     Poultry            73     1.30      1.02      0.50
     Hog                84     0.45      0.27      0.40
     Sheep              73     1.00      0.36      1.00
     Horse              60     0.70      0.25      0.60
*About 50% of the N is available the first year.

Losses of N sometimes exceeding 50% can occur during manure storage or following application to the surface of the soil. N loss is least when fresh manure is spread and worked into the soil immediately.

The above fertilizer recommendations are based on soil test values from the OSU Soil Testing Laboratory and on research conducted by the Crop and Soil Science and Horticulture Departments faculty, and is quoted form OSU Fertilizer Guide FG 55 for western Oregon recommendations and FG 72 for recommendations for eastern Oregon.


HARVESTING, HANDLING, AND STORAGE

The new pod stripping harvesters are used in harvesting snap peas. No swathing is needed. Pods must be protected from overheating. Picking speeds have to be adjusted to minimize pod damage.

Snap peas may yield approximately 3-5 tons per acre under ideal conditions. Yields decline rapidly as summer temperatures increase with yields of 2-4 tons per acre being more common. Processing yields and quality have generally been higher east of the Cascade Mountains, in the Columbia Basin, than in the Willamette Valley, where mold may be a problem when flower parts adhere to the pods and weather conditions favor mold.

Oriental pod peas may yield approximately 700 to 900 10-lb cartons per acre depending on the number of pickings. Oriental pod peas are hand harvested. Only limited success has been realized with machine harvest of Oriental pod peas using the new pod stripping harvesters. Hand harvest is slow and labor intensive.

In the Willamette Valley, edible pod pea harvest for processing may begin about June 1 and extend to September 30. The prime harvest period is from June 7 to September 20. In eastern Oregon processed edible pod pea harvest may begin about May 20 and extend to August 15. The prime harvest period in eastern Oregon is from June 10 to July 15.

The processor determines time of harvest of Oriental pod, or snap peas according to pod characteristics, the number of other fields ready for harvest, weather, soil conditions, and the processor's need for certain quality. Determining the proper time of harvest is a difficult decision that needs to balance the concern for highest quality (which occurs as pods reach near maximum diameter) with increased danger from the harvesting machinery causing pod splitting and shattering.

STORAGE (Quoted or modified from USDA Ag. Handbook 66 and other sources)

Edible pod peas tend to lose part of their sugar content, on which much of their flavor depends, unless they are promptly cooled to near 32 F and maintained at a relative humidity of 90-95%, after picking. Forced air cooling, using 32 F air with 90-95% humidity, is the preferred method of cooling since it does not result in surface moisture, and minimizes the risk of decay should subsequent temperatures during handling go over 34 F.

Hydrocooling may be used when the producer is close to the market, and temperature can be held to 32 F throughout all marketing steps to the consumer. With hydrocooling, edible pod peas packed in baskets can be hydrocooled from 70 to 34 F in about 12 minutes when the water temperature is 32 F. Vacuum cooling also is possible, but the edible pod peas must be pre-wet to obtain cooling similar to that by hydrocooling. After precooling, the peas should be packed with crushed ice (top ice) to maintain freshness and turgidity. Adequate use of top ice provides the required high humidity (95 %) to prevent wilting.

The ideal holding temperature at 32 F. Temperatures must not be allowed to go over 34 F when any surface moisture is present on the peas or rapid decay and deterioration will occur. Edible pod peas cannot be expected to keep in salable condition for more than 1 to 2 weeks even at 32 F unless packed in crushed ice. With ice, the storage period may be extended perhaps a week.

Research in England showed that the edible quality of green peas was maintained better when the peas were held in a modified atmosphere of 5 to 7 % carbon dioxide at 32 than in air for 20 days.


PACKAGING

Fresh-market edible-pod peas are hand harvested and the pods are commonly packaged in 30 to 32-lb bushel wirebound crates or cartons or 28 to 30-lb bushel baskets.


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